Resin materials for 3D-printing and milling of indirect restorations – Composition and leachables using an artificial saliva model

OBJECTIVE: Monomer leaching from resin-based restorations is a concern due to possible adverse effects on the oral environment. This study evaluated a validated artificial saliva model and a multi-instrument analytical workflow to characterize two liquid resins for 3D-printing, compare findings with manufacturers' SDSs, and determine leachable profiles from test specimens incubated in artificial saliva. METHODS: Liquid resins (Saremco print CROWNTEC, SCT; FREEPRINT® temp, FPT) were analyzed by UHPLC-HRMS and GC-MS. Disc-shaped specimens were 3D-printed and, as control, milled from Temp Premium Flexible (TPF) (n = 6). Samples were immersed in artificial saliva (surface area-to-volume ratio 1.2 cm²/mL, 37 °C). Aliquots were analyzed for methacrylate monomers and photoinitiators after 1 h, 24 h, 1 week, and 3 months using quantitative LC-MS/MS. Specimens incubated for 24 h and 3 months were further examined by untargeted UHPLC-HRMS. RESULTS: SDSs identified BisEMA as the main methacrylate in both resins, confirmed by UHPLC-HRMS. FPT also contained nondisclosed UDMA. Targeted analysis showed significantly higher concentrations of leachables (P < 0.05) from FPT than SCT or TPF at all time points. Untargeted analysis supported this, revealing the greatest number of leachables in FPT incubations, with at least 67 putative compounds. SIGNIFICANCE: Most residual methacrylate monomers elute within 24 h after 3D-printing. However, untargeted results suggest different leaching dynamics for other substances, highlighting the importance of broader analytical approaches in assessing biocompatibility.